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United States Patent |
5,585,543
|
Kao
|
December 17, 1996
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Alteration of plant self-compatibility using genetic manipulation of the
S-genes
Abstract
A method for altering self-compatibility/self-incompatibility in flowering
plants is presented. The method comprises manipulation of the plant genome
and production of the transonic plants. Abolishment of
self-incompatibility was achieved by inserting into plant genome as DNA
segment comprising anti-sense message of the allelic form of the S-gene
responsible for self-incompatibility. This insert prove to be satisfactory
to block expression of said allelic form of S-gene. Introduction of
self-incompatibility was achieved by inserting into plant genome DNA
construct comprising message coding for the S-protein responsible for
self-incompatibility.
Inventors:
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Kao; Teh-hui (State College, PA)
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Assignee:
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The Penn State Research Foundation (University Park, PA)
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Appl. No.:
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193826 |
Filed:
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February 9, 1994 |
Current U.S. Class: |
800/286; 435/320.1; 536/23.1; 536/23.6; 536/24.1; 800/298; 800/323.1 |
Intern'l Class: |
A01N 005/00; C12N 015/00; C12N 015/82 |
Field of Search: |
435/172.3,69.1,240.4,320.1
800/205,DIG. 40
536/23.6,23.1,24.1
|
References Cited
Other References
Toriyama et al (1991) Theor Appl Genet 81: 769-776.
Napoli et al (1990) The Plant Cell 2: 279-289.
Mariami et al (1992) Nature 357: 384-387.
Ai, Y. et al., Sex Plant Reprod., 1990, vol. 3, pp. 130-138.
Ioerger, T. R. et al., sex Plant Reprod. 1991, vol. 4, pp. 81-87.
Coleman, C. et al., Plant Molecul. Biol. 1992, vol. 18, pp. 725-737.
Heslop-Harrison (1975) Ann Rev. Plant Physiol 26: 403-425.
Nasrallah et al (1986) Tredsin Genet. (TIG) 2 (9): 239-244.
Matton et al (1994) Proc. Natl Acad Sci USA 91: 1992-1997.
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Primary Examiner: Fox; David T.
Assistant Examiner: McElwain; Elizabeth F.
Attorney, Agent or Firm: Monahan; Thomas J.
Goverment Interests
GOVERNMENT SPONSORSHIP
This invention was made with Government support under Grant No.
90-37261-5560 awarded by the U.S. Department of Agriculture and Grant No.
IBN-9220145 awarded by the National Science Foundation. The Government has
certain rights in the invention.
Claims
What is claimed is:
1. A solanaceous plant transformed with a gametophytic S-gene-specific
anti-sense polynucleotide or a gametophytic S-gene-specific
polynucleotide, wherein (1) transformation with said gametophytic
S-gene-specific anti-sense polynucleotide transforms a gametophytic
self-incompatible plant into a gametophytic self-compatible plant and (2)
transformation with said gametophytic S-gene-specific polynucleotide
transforms a gametophytic self-compatible plant into a gametophytic
self-incompatible plant, and wherein said gametophytic S-gene encodes
ribonuclease.
2. The plant of claim 1, wherein said gametophytic .epsilon.-gene-specific
anti-sense polynucleotide is a cDNA that is controlled by a gametophytic
S-gene promoter.
3. The plant of claim 2, wherein said cDNA is introduced to said plant as a
component of a plasmid.
4. The plant of claim 3, wherein said plasmid is pAS3.
5. The plant of claim 1, wherein said gametophytic S-gene-specific
polynucleotide is introduced to said plant as genomic DNA included in a
plasmid.
6. The plant of claim 5, wherein said genomic DNA comprises GS3 or a
segment thereof.
7. A method for promoting gametophytic self-compatibility or
self-incompatibility in a plant comprising regulation of gametophytic
S-locus activity, wherein said regulation of said gametophytic S-locus
activity causes loss-of-function or gain-of-function, wherein achieving
said loss-of-function or gain-of-function comprises introducing genetic
material comprising an S-locus gene into said plant,
wherein regulation for loss-of-function requires that said genetic material
comprise an anti-sense message of an allele of the gametophytic S-gene,
said allele being responsible for the self-incompatibility, wherein said
anti-sense message comprises a genetic sequence constructed using the
sequence or a portion of the sequence of said allele of the gametophytic
S-gene responsible for the incompatibility, said message having a
sufficient length to inhibit syntheses of active protein encoded by said
allele of the gametophytic S-gene.
8. The method of claim 7, wherein said message is constructed using a
sequence or sequence complementary to the hypervariable segment of said
alleles of the gametophytic S gene.
9. The method of claim 7, wherein said genetic material is a DNA construct
comprising anti-sense message and a regulatory region that promote
expression of said anti-sense message in said plant.
10. The method of claim 7, wherein said genetic material is a DNA construct
comprising the nucleotide sequence of an allele of the gametophytic S-gene
and a regulatory region that promotes expression of said nucleotide
sequence in said plant.
11. The method of claim 9, wherein preparation of said DNA construct
comprises the steps of:
(a) preparing a DNA segment that encodes the hypervariable region of the
gametophytic S-gene;
(b) ligating said hypervariable segment in the anti-sense orientation to a
promoter sequence to obtain a promoter-antisense fusion; and
(c) inserting said ligated promoter antisense fusion into a vector.
12. The method of claim 10, wherein preparation of said DNA construct
comprises the steps of:
(a) preparing a DNA segment that encodes the gametophytic S-gene;
(b) ligating said segment in the sense orientation to a promoter sequence
to obtain a promoter-sense fusion; and
(c) inserting said ligated promoter-sense fusion into a vector.
13. The method of claim 7, wherein said anti-sense message comprises SEQ ID
NO:1 or SEQ ID NO:2.
14. The method of claim 10, wherein said genetic material comprises the
complement to SEQ ID NO:1 or SEQ ID NO:2.
Description
BACKGROUND OF THE INVENTION
The present invention relates to the genetic manipulation of the plants.
More specifically it relates to the regulation of the serf-pollination in
flowering plants.
By the way of background, for over 130 years, since Darwin observed that
some plants can fertilize themselves with their own pollen while others
cannot, scientists have been trying to understand exactly what controls
this aspect of plant mating. The present invention, which describes a
method of altering the nature of this mating, provides the first direct
evidence confirming a theory of genetic self-incompatibility that is the
foundation of research in plant genetics.
The cornerstone of this theory is self-incompatibility, the genetic barrier
to inbreeding in flowering plants. In the simplest cases it is controlled
by a single locus, the S-locus, which has a large number of alleles. In
gametophytic type self-incompatibility, fertilization is blocked when the
S-allele expressed by the pollen matches at least one of the two alleles
carded by the pistil. The present invention describing the alteration of
the self-incompatibility in petunia plants can prove especially useful in
many flowering plants, either to introduce or to abolish
self-incompatibility.
The ability to prevent plants from fertilizing themselves could double the
yield and reduce by one-third to two-thirds the labor costs involved in
hybrid seed production. Virtually all commercially important vegetables
and many important flowers are produced from F1 hybrid seeds, the result
of crossing two purebred plant lines. In order to assure the uniformity of
hybrid seeds, growers typically must remove by hand the pollen-producing
organs from the seed-producing parent plants, then discard the seed
produced by the pollen parents--sacrificing half the seed crop. If the
plants were 100% self-incompatible, you could harvest seed from every
plant while using much less costly and more efficient fertilization
procedures. In addition, the ability to control the serf-compatibility
could provide the key to producing hybrids in many crops where this
technique previously has been either inefficient or impossible.
Growers of self-incompatible crops could benefit from the possibility of
changing the nature of the plants by transforming them into
self-compatible plants. Because of this self-incompatibility, commercial
apple growers typically mix, in a single orchard block, three varieties
that they carefully select to provide sources of compatible pollen.
Cultivation of a single self-compatible variety would increase efficiency
by reducing several cultural and harvesting problems.
Confirmation that the S gene encodes the key protein in self-recognition,
which is the core of the present invention, is an important step for the
scientists who have published analyses based on that assumption. Many
generations of scientists have devoted their lives to understanding the
system of self-incompatibility in plants. The Applicant has added
something to this effort that others have been seeking for half a century.
The invention herein described contributes to the understanding of this
biological process bringing it into the era of modern molecular biology.
SUMMARY OF THE INVENTION
In accordance with the present invention, a method to alter the
self-incompatibility in the flowering plants by controlling the activity
of the S-locus is presented.
A protein identified in the early 1980s seemed to be the predicted S
protein, but the strongest clues until now were only from indirect
evidence. By harnessing standard genetic-engineering techniques, the
Applicant was able to neutralize a particular allelic form of the S-gene
in a group of petunia plants, reversing their inherited inability to
fertilize themselves and enabling them to produce seeds. The Applicant
also inserted a particular allele of an S-gene into the genome of another
group of plants, giving them the ability to reject pollen with a specific
genetic identity.
Experiments were performed to show that a plant's ability to produce seeds
when self pollinated depends on the presence or absence of an particular
S-gene. In one experiment, an S gene was disabled in a line of
self-incompatible plants, then fertilization with their own pollen was
attempted. The reasoning behind this approach is that if an S protein is
required for self-incompatibility interactions between pistil and pollen,
then inhibition of its synthesis should lead to the breakdown of self
incompatibility.
Each plant has two varieties of the S gene, called S alleles, which it
inherits from the parent plants. The Applicant used petunia plants that
had alleles called S2 and S3. A genetic engineering technique was used to
produce an "antisense" message of a segment of the S3 allele whose DNA
sequence order is the reverse of that of a normal S3 allele's.
Next, the antisense S3 allele was incorporated into a bacterium that can be
used to infect petunia leaves. From these leaves grew transgenic plants
containing S2, S3, and antisense S3. Antisense RNA was able to block the
synthesis of protein from sense RNA.
These transgenic plants were tested and found that they were not producing
any S3 protein. Thereafter, attempts were made to fertilize them with S3
pollen. A normal plant with S2 and S3 alleles, when pollinated with S3
pollen, will reject the pollen because the S allele types match. The
flower's pistil recognizes the pollen as `self pollen,` fertilization
fails, and the plant does not produce seeds. Obtained transgenic petunias
produced the same large number of seeds as you would get from compatible
pollination, showing that they had lost the ability to reject self pollen.
This is the first successful attempt to use the antisense approach in any
self-incompatible plant species.
In another experiment, the Applicant put an S3 gene into petunias that
contained S1 and S2 alleles. A normal plant with S1 and S2 alleles will
accept S3 pollen because the S3 allele carried by the pollen is different
from the S1 and S2 alleles carried by the flower's pistil. However, it was
found that some of the transgenic plants produced no seeds at all when
pollinated with S3 pollen. This is a first direct evidence that by genetic
manipulation one can introduce self-incompatibility.
The transgenic plants that failed to produce any seeds at all had normal
levels of S3 protein for a plant containing an S3 gene, which enabled them
to acquire the ability to completely reject S3 pollen. Some transgenic
plants that produced a few seeds when pollinated with S3 pollen had levels
of S3 protein that were much lower than normal, and those transgenic
plants producing the most seeds did not have any detectable amount of S3
protein. This experiment shows that S-protein levels alone control a
plant's ability to reject its own pollen--or pollen whose S allele type is
identical to one of those contained in the flower's pistil.
OBJECTS OF THE INVENTION
It is an object of this invention to present a method for altering the
self-incompatibility in flowering plants.
Another object of this invention is to provide a method for controlling the
activity of the S locus involved in the self-pollination of plants.
These and other objects and advantages of this invention over prior art and
a better understanding of its use will become readily apparent from the
following description and are particularly delineated in the appended
claims.
DESCRIPTION OF THE DRAWINGS
FIGS. 1a and 1b: FIG. 1a presents a diagram of Antisense construct.
FIG. 1b presents a genomic Southern blot. Lane 1: parental S.sub.2 S.sub.3
plant; lane 2: AS-37; lane 3: AS-4; lane 4: AS-14, lane 5: AS-27.
FIGS. 2a and 2b: FIG. 2a presents Northern blots. Two identical RNA blots
each containing total pistil RNA (10 .mu.g per lane) of a parental S.sub.2
S.sub.3 plant (lane 1), AS-39 (lane 2), AS-14 (lane 3), and AS-27 (lane
4).
FIG. 2b presents FPLC profile.
FIGS. 3a and 3b: FIG. 3a presents a schematic representation of the genomic
DNA used in transformation experiments.
FIG. 3b presents a genomic Southern blot.
FIGS. 4a and 4b: FIG. 4a presents a Northern blot.
FIG. 4b presents FPLC profiles of the proteins.
DETAILED DESCRIPTION OF THE INVENTION
The present invention describes the evidence of correlation between
self-compatibility and S-genes in petunia plants. During the course of
detailed studies involving the investigation of plant
self-incompatibility, the involvement of proteins encoded by S-genes was
demonstrated. The support for this new finding and ways of using it
commercially are described herein.
A detailed embodiment of the present invention involving petunia plants is
herein disclosed. However it is understood that the preferred embodiment
is merely illustrative of the invention which may be embodied in various
forms and applications. Accordingly, specific structural and functional
details disclosed herein are not to be interpreted as limiting, but merely
as a support for the invention as claimed and as appropriate
representation for the teaching one skilled in the an to variously employ
the present invention in any appropriate embodiment.
The applicant used both loss-of-function and gain-of-function approaches to
ascertain whether the P. inflata S-proteins previously identified.sup.9 do
indeed control self-incompatibility interactions between pollen and
pistil. In the former approach, he introduced antisense S.sub.3 -cDNA
under the control of the promoter of the S.sub.3 -gene into P. inflata
plants of S.sub.2 S.sub.3 genotype by Agrobacterium-mediated
transformation (FIG. 1a). This allowed him to determine whether inhibition
of S.sub.3 -protein synthesis in the pistil abolished the ability of the
transgenic plants to reject S.sub.3 -pollen.
Forty-seven independent transgenic plants were self-pollinated to determine
whether their self-incompatibility behavior had been affected. Thirty
plants were found to set variable numbers of seeds, and 6 of them
consistently produced a number of seeds comparable to that obtained from
compatible pollination of P. inflata plants (approximately 200 per fruit).
These 6 transgenic plants (AS-4, AS-14, AS-23, AS-27, AS-35, and AS-37)
were chosen for further analysis. Genomic blot analysis of 4 of the plants
revealed that, in addition to the 11.5 kb DNA fragment corresponding to
the endogenous S.sub.3 -gene, they contained one to three insertions of
the transgene (FIG. 1b).
To determine whether the breakdown of self-incompatibility in the 6
self-compatible transgenic plants resulted from loss of their ability to
reject S.sub.3 -pollen, these plants were pollinated with pollen from
S.sub.2 S.sub.3 and S.sub.2 S.sub.2 tester plants. AS-14, AS-23, and AS-37
rejected pollen from S.sub.2 S.sub.2 plants, but accepted pollen from
S.sub.2 S.sub.3 plants, indicating that S.sub.3 -allele had been rendered
nonfunctional, but S.sub.2 -allele was not affected. AS-4, AS-27, and
AS-35 accepted pollen from both S.sub.2 S.sub.2 and S.sub.2 S.sub.3
plants, indicating that, in addition to S.sub.3 -allele, S.sub.2 -allele
had also been rendered nonfunctional. AS-39, a self-incompatible
transgenic plant, rejected pollen from both S.sub.2 S.sub.2 and S.sub.2
S.sub.3 plants.
Next the Applicant investigated whether the inability of the 6
self-compatible transgenic plants to reject S.sub.2 - or S.sub.3 -pollen
was caused by inhibition of S.sub.2 - or S.sub.3 -protein synthesis. As
shown in FIG. 2a, AS-14, which rejected S.sub.2 -allele but failed to
reject S.sub.3 -allele, contained a normal level of S.sub.2 -RNA, but a
nondetectable level of S.sub.3 -RNA; AS-27, which failed to reject either
S.sub.2 - or S.sub.3 -allele, contained nondetectable levels of S.sub.2
-RNA and S.sub.3 -RNA; AS-39, which rejected both S.sub.2 - and S.sub.3
-alleles, contained normal levels of S.sub.2 - and S.sub.3 -RNA.
The applicant then determined the amounts of S.sub.2 - and S.sub.3
-proteins in the pistils of the 6 self-compatible and 7 self-incompatible
transgenic plants, and 7 parental S.sub.2 S.sub.3 plants (FIG. 2b).
Profile a in FIG. 2b is representative of these parental S.sub.2 S.sub.3
plants. AS-14, AS-23, and AS-37 all contained normal amounts of S.sub.2
-protein, but drastically reduced amounts of S.sub.3 -protein (profile c
in FIG. 2b shows AS-14). The amounts of both S.sub.2 - and S.sub.3
-proteins were drastically reduced in AS-4, AS-27, and AS-35 (profile d
shows AS-27). In fact, the amounts of S.sub.3 -protein in the former 3
plants, and the amounts of S.sub.2 - and S.sub.3 -proteins in the latter 3
plants were lower than those present in immature buds which are fully
receptive to serf pollen.sup.9. The amounts of S.sub.2 - and S.sub.3
-proteins of the 7 self-incompatible transgenic plants were comparable to
those of the parental S.sub.2 S.sub.3 plants (profile b shows AS-39).
The effect of the antisense S.sub.3 -gene was inheritable, because
self-compatible plants were found in selfed progeny of AS-14 and AS-27. As
in the parental transgenic plants, the amounts of S.sub.2 - and S.sub.3
-proteins also correlated perfectly with breeding behavior (results not
shown). Thus, it was concluded from the antisense experiments that
S-proteins are necessary for the pistil to reject self pollen.
The applicant used the gain-of-function approach to ascertain whether
S-proteins alone are sufficient for the pistil to reject serf pollen. A
3.6 kb DNA fragment (FIG. 3a) containing the gene for S.sub.3
-protein.sup.9, 18 was introduced into P. inflata plants of S.sub.1
S.sub.2 genotype, and it was determined whether expression of the S.sub.3
-gene could confer on the transgenic plants a new S.sub.3 -allele
specificity. Eighty-one transgenic plants were pollinated with pollen from
S.sub.3 S.sub.3 plants, and 4 plants, GS3-13, GS3-16, GS3-41, and GS3-55,
were found to completely reject S.sub.3 -pollen. The rest set fruits of
variable sizes with seed numbers ranging from 20 to 200, indicating that
they were either partially or fully compatible with S.sub.3 -pollen.
The 4 transgenic plants that completely rejected S.sub.3 -pollen also
rejected pollen from S.sub.1 S.sub.2 plants. However, they set large
fruits when selfed at the immature-bud stage when self-incompatibility is
not yet expressed. Thus, the failure of the 4 plants to set fruits when
pollinated with S.sub.1 -, S.sub.2 - and S.sub.3 -pollen was a true
self-incompatible response, and not due to female sterility resulting from
tissue culture manipulations.
Genomic blot analysis revealed that all 4 plants contained a single insert
of the transgene (FIG. 3b). Two other transgenic plants were also included
in the analysis: GS3-75, a plant partially compatible with S.sub.3 -pollen
(producing approximately 50 seeds per fruit, and GS3-113, a plant fully
compatible with S.sub.3 -pollen (producing approximately 200 seeds per
fruit). GS3-75 contained two inserts and GS3-113 contained one insert
(FIG. 3b).
To investigate whether the new S.sub.3 -allele specificity acquired by the
4 transgenic plants resulted from expression of the S.sub.3 -transgene in
the pistil, the applicant first examined the level of S.sub.3 -RNA in the
pistils of representative transgenic plants. As shown in FIG. 4a, GS3-16
and GS3-55, which completely rejected S.sub.3 -pollen, contained a normal
level of S.sub.3 -RNA; GS3-75 and GS3-109, which were partially compatible
with S.sub.3 -pollen, contained approximately 30% the normal level of
S.sub.3 -RNA; GS3-113, which was fully compatible with S.sub.3 -pollen,
did not contain any detectable S.sub.3 -RNA.
The Applicant examined the mounts of S.sub.3 -protein in the pistils of 31
transgenic plants which included all the ones described above (FIG. 4b).
All 4 plants that completely rejected S.sub.3 -pollen were found to
produce a normal level of S.sub.3 -protein, in addition to producing
normal levels of S.sub.1 - and S.sub.2 -proteins (compare the profile of
GS3-55 with those of S.sub.1 S.sub.2 and S.sub.2 S.sub.3 plants). All 17
plants that were partially compatible with S.sub.3 -pollen produced the
amounts of S.sub.3 -protein that were invariably much lower than normal
(compare the profile of GS3-75 with that of GS3-55), and were comparable
to or less than those present in immature buds of nontransgenic plants.
All 10 plants that were fully compatible with S.sub.3 -pollen did not
produce any detectable amount of S.sub.3 -protein (see the profile of
GS3-113). Thus, it was concluded that the production of a normal level of
S.sub.3 -protein in the pistil of the 4 transgenic plants conferred on
them the ability to completely reject S.sub.3 -pollen. The finding that
low level expression of the S.sub.3 -transgene in the pistil of mature
flowers was not sufficient for rejection of S.sub.3 -pollen is similar to
the previous findings that a low level of S-gene expression in immature
buds of Petunia plants correlated with their inability to reject self
pollen.sup.9, 19.
Both the S.sub.3 -transgene and the antisense S.sub.3 -gene did not affect
the self-incompatibility behavior of the pollen of the transgenic plants
(data not shown). These results are consistent with the model of the
S-locus proposed by Lewis which states that separate but closely linked
genes control the self-incompatibility phenotype of the pollen and
pistil.sup.20.
In conclusion, the results presented in this invention provide direct in
vivo evidence that the S-proteins of P. inflata are necessary and
sufficient for the pistil to reject self pollen. This study also
demonstrates the feasibility of using the antisense RNA approach to break
down self-incompatibility. Furthermore, demonstration that the S-phenotype
of a self-incompatible plant can be altered by the introduction of a
single gene, the S-gene, should allow future dissection of the functional
domains of the S-protein through mutagenesis studies.
EXAMPLE 1
Transformation of P. inflata Plants with Antisense S.sub.3 -gene, and
Analysis of Transgenic Plants for Presence of the Transgene
Antisense Construct
The construct is presented in FIG. 1a. The promoter used to express the
antisense S.sub.3 -cDNA was contained in a DNA fragment spanning from
position -2,032 bp to position +15 bp of S.sub.3 -gene.sup.18. This DNA
fragment had already been shown to confer pistil expression of the gene
encoding b-glucuronidase (GUS) in transgenic P. inflata plants
(unpublished results). The EcoRI-NdeI fragment of the S.sub.3 -cDNA used
in the construct contained approximately 70% of the full-length S.sub.3
-cDNA previously reported.sup.9. Sense S.sub.3 -cDNA is indicated by an
arrow pointing to the right; antisense S.sub.3 -cDNA is indicated by an
arrow pointing to the left. The transcriptional termination signal was
provided by the nopaline synthase terminator (nos-ter) present on a binary
Ti-plasmid pBI101 (Clontech). The NPTII gene, which encodes neomycin
phosphotransferase and confers kanamycin resistance in transgenic plants,
is expressed by the promoter of the nos gene (nos-pro). The 2,047 bp
S.sub.3 -promoter fragment was cloned into the HindIII and SmaI sites of
pBluescript KS+ (Stratagene) to yield pS3. pS3 was digested with BamHI,
and Klenow enzyme was used to create blunt ends. In the same fashion,
blunt ends were created on an EcoRI-NdeI fragment of the S.sub.3 -cDNA,
and this fragment was ligated in antisense orientation to the S.sub.3
-promoter in pS3. The S.sub.3 -promoter-S.sub.3 -cDNA fusion product was
released by double digestion with XhoI and SacI, and the fragment was
ligated into the SalI and SacI sites of pBI101. (The GUS gene present on
pBI101 was removed during this step.)
Insertion of the Plasmid into a Plant
The recombinant Ti-plasmid, designated pAS3, was electroporated into
Agrobacterium tumefaciens strain LBA4404. Leaf discs of P. inflata with
S.sub.2 S.sub.3 genotype were infected with the Agrobacterium by the
co-cultivation method.sup.21 on MS medium supplemented with
benzylaminopurine (1.0 mg/L) and naphthalene acetic acid (75 mg/L). Shoots
were regenerated on fresh MS medium.sup.22 supplemented with kanamycin
(100 mg/ml) and carbenicillin (500 mg/ml). Regenerated shoots were
transferred to hormone-free MS medium containing the same concentrations
of antibiotics to induce root formation.
Detection of the Protein Level in the Transgenic Plants
The level of protein present in the transgenic plants is represented in
FIG. 1b, which is a radiograph of a filter from a genomic Southern blot.
The filter containing EcoRI digests of genomic DNA was hybridized to a
probe containing the full-length S.sub.3 -cDNA.sup.9. Genomic DNA was
isolated from 2 g of frozen leaves with an Elu-Quick kit (Schleicher &
Schell) following the manufacturer's protocol. Genomic DNA (5 mg) was
digested with EcoRI, separated on a 0.8% agarose gel, and transferred to a
Biotrans (+) nylon membrane (ICN). The membrane was prehybridized in a
solution containing 5.times.SSC, 5.times.Denhardt's, 0.1% SDS, and 100
mg/ml of sheared and denatured fish sperm DNA for 2 hours at 65.degree. C.
Hybridization was carried out in the same solution with the addition of
.sup.32 P-labelled S.sub.3 -cDNA for 16 hours at 65.degree. C. The
membrane was washed in 0.1.times.SSC and 0.1% SDS at 65.degree. C. for 1
hour and exposed on X-ray film with an intensifying screen for 2 days at
-70.degree. C.
EXAMPLE 2
Analysis of the Amounts of S.sub.2 - and S.sub.3 -RNA, and S.sub.2 - and
S.sub.3 -Proteins in a Parental S.sub.2 S.sub.3 Plant and Transgenic
Plants
Analysis of the Amounts of RNA
The analysis of the amount of the RNA was performed using Northern blots.
The results are presented in FIG. 2a. Two identical RNA blots each
containing total pistil RNA (10 .mu.g per lane) of a parental S.sub.2
S.sub.3 plant, AS-39, AS-14, and AS-27, were hybridized with two
radiolabelled probes separately: S.sub.2 -oligo, an oligonucleotide
specific to sense S.sub.2 -RNA, and S.sub.3 -oligo, an oligonucleotide
specific to sense S.sub.3 -RNA. After autoradiography, the bound
radiolabelled probes were removed from the blots, and the blots were
hybridized with the third probe, rDNA, which encodes 25S rRNA of P.
inflata. That step was performed in order to eliminate a possibility that
a lack of signal is due to RNA degradation. Total RNA was isolated from
pistils as previously described.sup.10. RNA samples were electrophoresed
on 1.2% agarose/formaldehyde gels and transferred to Biotrans (+)
membranes. The probe specific to sense S.sub.2 -RNA was a 51-mer with
sequence: 5'-CAGAACATTGATTATATTATCTTCTTTFFAAAACGCGAATACTTGTCGCCAGT-3'
(SEQ. ID NO:1). This sequence is complementary to a segment of S.sub.2
-cDNA encoding amino acid residues 48 to 64 of S.sub.2 -protein.sup.9,
which is located in the hypervariable region HVa of S-proteins.sup.25. The
probe specific to sense S.sub.3 -RNA was a 54-mer with sequence:
5'-CAAATCATTGACAATTCTATCTTTTAAGCTGAACGACACAAACTTATCTCCATC-3' (SEQ. ID
NO:2). This sequence is complementary to a segment of S.sub.3 -cDNA
encoding amino acid residues 48 to 65 of S.sub.3 -protein.sup.9, which is
also located in the HVa region. The two oligonucleotides were .sup.32
P-labelled at their 5' ends with T4 polynucleotide kinase. For
hybridization with S.sub.2 - or S.sub.3 -oligo, the membranes were
prehybridized as described in FIG. 1b, except at 45.degree. C. for 2 hr,
and hybridized in the prehybridization solution containing S.sub.2 - or
S.sub.3 -oligo probe at 45.degree. C. overnight. The membranes were twice
washed in 0.1.times.SSC, 0.1% SDS at room temperature for 10 min each, and
then washed with the same solution at 40.degree. C. for 5 min.
Autoradiography was carded out at -70.degree. C. for 16 hr with an
intensifying screen. The bound radiolabelled probes were removed from the
membranes by boiling in 0.1.times.SSC and 0.1% SDS. For hybridization with
the rDNA probe, the membranes were prehybridized as described for FIG. 1b
in Example 1, and hybridized with the prehybridization solution containing
.sup.32 P-labelled rDNA probe at 65.degree. C. overnight. The membranes
were washed in 0.1.times.SSC, 0.1% SDS at 65.degree. C. for 1 hr, and
autoradiographed at -70.degree. C. for 1 hr with an intensifying screen.
Analysis of the Amounts of S.sub.2 - and S.sub.3 -Proteins
The protein level was measured using FPLC profiles. The results are
presented on FIG. 2b. S.sub.2 - and S.sub.3 -proteins cannot be separated
by SDS-PAGE due to their similar molecular weight.sup.9, but can be
separated from each other and from other pistil proteins by
cation-exchange chromatography on a Mono-S column using the FPLC system
(Pharmacia).sup.14. The majority of pistil proteins flowed through during
loading and washing of the column with 50 mM sodium phosphate (pH 6.0).
The bound proteins that were eluted with the salt gradient consisted
mainly of S-proteins and a pistil-specific ribonuclease, X2.sup.14, 23.
The observed concomitant reduction of the level of S.sub.2 -protein in
AS-27 (as well as in AS-4 and AS-35, not shown) and of the level of X2 in
AS-27 by the antisense S.sub.3 -gene may be due to the sequence similarity
between the 585 bp fragment of S.sub.3 -cDNA used in the antisense
construct and the corresponding regions in the genes for S.sub.2
-protein.sup.9 and RNase X2.sup.23. It has been previously observed that
antisense RNA can inhibit the mRNA production from a target gene, as well
as from genes with sequence similarity to the target gene.sup.24.
Pistils were collected from freshly opened flowers of each plant and stored
at -70.degree. C. until use. Forty milligrams of pistils from each plant
were ground to a fine powder in liquid nitrogen, with further grinding
after the addition of 1 ml of the extraction buffer containing 50 mM
Tris-HCl, pH 8.5, 10 mM EDTA, 1 mM PMSF, 1 mM CaCl.sub.2, and 1 mM DTT.
The crude extract was centrifuged at 12,000 g for 10 min, and the
supernatant filtered through a 0.45 mm Millex-GV filter (Millipore) to
remove unsedimented fine particles. The filtrate was applied to a Mono-S
column (HR 5/5) which had been equilibrated with 50 mM sodium phosphate
(pH 6.0). The bound proteins were eluted with a linear gradient of 0 to
500 mM NaCl in the same buffer at a flow rate of 0.5 ml/min. Proteins were
monitored at A.sub.280 nm with the sensitivity of the detector set to 0.1
AUFS. No discernible differences in the FPLC profiles for each plant were
detected when two separate pistil extractions were used. The profile shown
for each plant is one of the two runs.
EXAMPLE 3
Transformation of P. inflata Plants with S.sub.3 -gene, and Analysis of
Transgenic Plants for Presence of the Transgene
Transformation of P. inflata Plants with S.sub.3 -gene
Schematic representation of the genomic DNA used in transformation
experiments is presented in FIG. 3a. The DNA fragment, GS3, spans from
position -2,032 bp to position +1,553 bp of the S.sub.3 -gene.sup.18. Open
boxes denote the exons; the hatched box denotes the intron. Restriction
enzyme sites are indicated with one-letter abbreviations: H, HindIII; N,
Nde I; S, Stu I; B, Bsu 96I. The 3.6 kb genomic DNA (GS3) was released
from the cloning vector pBluescript KS+ (Stratagene) by digestion with Xho
I and Sac I, and the fragment was ligated into Sal I and Sac I sites of a
binary Ti-plasmid vector pBI101. The GUS gene present on pBI101 was
removed during this step. The recombinant Ti-plasmid was introduced into
P. inflata plants by Agrobacterium-mediated transformation as described in
FIG. 1b.
Analysis of Transgenic Plants for Presence of the Transgene
The analysis was performed using the genomic Southern blot technique. The
falter containing HindIII digests of genomic DNA was hybridized with a
radiolabelled probe of the full-length S.sub.3 -cDNA.sup.9. The genomic
DNA was isolated from 1 nontransgenic plant S.sub.1 S.sub.2 and 6
transgenic plants, as indicated above the blot. The results are presented
on FIG. 3b. The arrow marks a weakly hybridizing DNA fragment of 9.9 kb
which corresponds to the endogenous S.sub.2 -gene. The endogenous S.sub.1
-gene did not cross-hybridize with the S.sub.3 -cDNA probe under the
conditions used. The DNA size markers are indicated. Two fragments seen in
GS3-75 each resulted from one cut by HindIII within the integrated S.sub.3
-gene and a second cut in the genome. Genomic DNA was isolated from 2 g of
frozen leaves as described in Example 1 for FIG. 1b. Genomic DNA (5 mg)
was digested with HindIII, separated on a 0.8% agarose gel, and
transferred to a Biotrans (+) nylon membrane (ICN). Prehybridization,
hybridization, and washing of the falter were carded out as described in
Example 1 for FIG. 1b. The filter was exposed on X-ray film at -70.degree.
C. for 48 h with an intensifying screen.
EXAMPLE 4
Analysis of the Amounts of S.sub.3 -RNA and S.sub.3 -Protein
Analysis of the Amounts of S.sub.3 -RNA
The amount of the RNA was measured by Northern blot. The results are
presented in FIG. 4a. Each lane of the RNA blot contains 10 .mu.g of total
pistil RNA. Of the 7 plants analyzed, S.sub.2 S.sub.3 and S.sub.1 S.sub.2
are nontransgenic plants and the other 5 are transgenic plants. The blot
was first hybridized with a radiolabelled oligonucleotide probe (S3)
specific to S.sub.3 -RNA. After autoradiography, the bound radiolabelled
probe was removed, and the blot was hybridized with a second probe (rDNA)
which encodes 25S rRNA of P. inflata. The absence of a hybridizing
fragment in the S.sub.1 S.sub.2 sample confirms the specificity of the S3
probe used. The procedures for isolation of total RNA and for Northern
analysis were identical to those described in Example 2. The S.sub.3 -RNA
specific probe and the rDNA probe used were described in Example 2. After
washing, the amount of radioactivity associated with each hybridizing band
was determined using a Betagen Betascope. The relative amount of S.sub.3
-RNA in each transgenic plant to that of S.sub.2 S.sub.3 plant was
calculated after correction for the differences in the total amount of
rRNA. The filters were then exposed on X-ray films at -70.degree. C. for
30 min (rDNA probe) and 5 h (S3 probe) with intensifying screens.
Analysis of the Amounts of S.sub.3 -protein
The FPLC was used to measure the mounts of proteins. The profiles are
presented in FIG. 4b. Total pistil protein of each plant was separated by
a Mono-S column. Only the S-protein fractions are shown. Extractions of
total pistil protein and conditions for column chromatography were as
described in Example 2, except for three modifications: 5 mg of the
pistils from each plant were used for extractions; the gradient was 2
times shallower; proteins were monitored with the sensitivity of the
detector set to 0.02 AUFS. In addition, a different Mono-S column with the
same dimension was used. Some of these modifications may account for
differences in the salt concentration at which the same S-protein was
eluted in the profiles shown here and in those shown in Example 2.
Thus, while I have illustrated and described the preferred embodiment of my
invention, it is to be understood that this invention is capable of
variation and modification, and I, therefore, do not wish or intend to be
limited to the precise terms set forth, but desire and intend to avail
myself of such changes and alterations which may be made for adopting the
invention of the present invention to various usages and conditions.
Accordingly, such changes and alterations are properly intended to be
within the full range of equivalents and, therefore, within the purview of
the following claims. The terms and expressions which have been employed
in the foregoing specification are used therein as terms of description
and not of limitation, and thus there is no intention in the use of such
terms and expressions of excluding equivalents of features shown and
described or portions thereof, it being recognized that the scope of the
invention is defined and limited only by the claims which follow.
Thus is described my invention and the manner and processing of making and
using it in such full, clear, concise, and exact terms so as to enable any
person skilled in the art to which it pertains, or with which it is most
nearly connected, to make and use the same.
References
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Genetics (eds Frankel, R., Gall, G. A. E. & Linskens, H. F.) (Springer,
Berlin, 1977)
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(eds Frankel, R., Gall, G. A. E. & Linskens, H. F.) (Springer, Berlin,
1977)
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(1981)
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4, 81-87 (1991)
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SEQUENCE LISTING
(1) GENERAL INFORMATION:
(iii) NUMBER OF SEQUENCES: 2
(2) INFORMATION FOR SEQ ID NO:1:
(i) SEQUENCE CHARACTERISTICS:
(A) LENGTH: 51 base pairs
(B) TYPE: nucleic acid
(C) STRANDEDNESS: single
(D) TOPOLOGY: linear
(ii) MOLECULE TYPE: DNA (genomic)
(xi) SEQUENCE DESCRIPTION: SEQ ID NO:1:
CAGAACATTGATTATATTATCTTCTTTAAAACGCGAATACTTGTCGCCAGT51
(2) INFORMATION FOR SEQ ID NO:2:
(i) SEQUENCE CHARACTERISTICS:
(A) LENGTH: 54 base pairs
(B) TYPE: nucleic acid
(C) STRANDEDNESS: single
(D) TOPOLOGY: linear
(ii) MOLECULE TYPE: DNA (genomic)
(xi) SEQUENCE DESCRIPTION: SEQ ID NO:2:
CAAATCATTGACAATTCTATCTTTTAAGCTGAACGACACAAACTTATCTCCATC54
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